用视密度加权平均二阶矩模型模拟旋流两相流动

SIMULATION OF SWIRLING GAS-MRRTICLE FLOWS USING A MASS-WEIGHED MERAGED UNIFIED SECONDORDER MOMENT TWO-PHASE TURBULENCE MODEL

本文用视密度加权平均代替时平均，建立了视密度加权平均的统一二阶矩两相湍流模型方程组（ＭＵＳＭ），其中用体积分数代替了数密度，用颗粒驰豫时间作为封闭两相脉动速度关联方程耗散项的时间尺度，并引入了颗粒视在的气体速度脉动的输运方程。用ＭＵＳＭ模型模拟了旋流数为０．４７的气粒两相流动。并和实验结果及时间平均的ＵＳＭ模型的模拟结果进行了对照，两种模型均能较好地预报的两相的轴向和切向速度，轴向和切向脉动速度。此外，ＭＵＳＭ模型可以减少所用方程数，节省计算量。因此视密度加权平均的统一二阶矩两相湍流模型是一种对时间平均的统一二阶矩模型的改进，今后可以进一步扩大应用。

A mass-weighed averaged second-order moment (MUSM) two-phase turbulence model is proposed. The volume fraction is used instead of particle number density. The particle relaxation time is used to close the dissipation term in the transport equation of two-phase fluctuation velocity correlation. The gas fluctuation velocity seen by particles is taken into account. The MUSM model is used to simulate swirling gas-particle flows with a swirl number of s=0.47. The MUSM predictions are compared with those using the time-averaged second-order moment (USM) model and with the PDPA measurements made in references. The results show that the MUSM and USM models give almost the same results for particle time-averaged and fluctuation velocities, if the same closure method is used in these models. However, compared with the USM model using a simplified closure with no dissipation in the two-phase fluctuation velocity correlation equations, the MUSM model gives some improvement. For example, near the inlet region the MUSM model gives the particle axial velocity in better agreement with experiments than the USM model. The MUSM model properly predicts the lagging of particle tangential fluctuation velocity behind the gas one, observed by measurements. Besides, the MUSM model needs fewer equations than the USM model. Hence the MUSM model can be considered as an improvement to the USM model and it can be further applied and tested.